The electrophoresis method is extremely effective in analyzing DNA, a protein expressed in cancer, and the like, from a micro amount of blood which has been collected from a subject. With the electrophoresis method, a sample (blood, or the like) added with a fluorescent dye is mixed into a buffer liquid containing a gel. Thereafter, this liquid is supplied to one end of a channel (micro-channel) having a fine cross-sectional area, and a voltage is applied across both ends of the channel, then, the charged molecule is gradually migrated toward the other end in the channel by the electric field, however, the greater the molecular weight of a molecule, the slower the migration speed therefore will be. Therefore, after the lapse of a predetermined time, the reaching position (migration distance) of each particular type of molecule varies in a long channel.
In order to determine this migration distance, the sample is mixed with a specific fluorescent dye, and this fluorescent dye is carried by a molecule, DNA, or the like, which is to be analyzed. This fluorescent dye, when irradiated with an excitation light, emits fluorescence having a specific wavelength (color) which is longer than that of this excitation light, and therefore, by examining the distribution of this fluorescence in the channel after the lapse of a predetermined time, the migration distance can be measured. Thereby, it is possible to perform, for example, composition analysis of a molecule or DNA contained in the sample, and the like. Thus, in order to perform an analysis with high sensitivity, there is the need for a technique which allows fluorescence in the fine channel to be detected with high accuracy.
For improving the sensitivity of such electrophoresis method, Patent Document 1 discloses a technique with which the channel is covered with a diffraction grating having a light scattering function to thereby enhance the efficiency of detection of fluorescence emitted by a fluorescent dye. However, with this method, it is particularly difficult to make the analyzing apparatus including the channel compact.
Contrarily to this, with the method disclosed in Patent Document 2, the configuration of the analyzing apparatus including a micro-channel is the same as that of the conventional one, but the buffer liquid is mixed with ZnO powder (ZnO fine particles) to thereby substantially enhance the intensity of the fluorescence. In this case, the excitation light is multiple-scattered by the colloidal particles formed caused by the ZnO powder, thereby the intensity of the excitation light irradiated on the fluorescent dye molecules being substantially enhanced. In addition, the light corresponding to the forbidden bandwidth of ZnO is ultraviolet radiation, and thus the excitation light on the fluorescent dye and the fluorescence thereof will not be absorbed by the ZnO fine particles. Therefore, the substantial intensity of the fluorescence emitted from the fluorescent dye can be enhanced. By using this method, it is possible to provide a detection sensitivity which is, for example, double or more times as high as that which has been conventionally available.